Chemokine receptors/HIV-1 coreceptors are important for understanding viral entry and HIV-1 pathogenesis. However, little is known about their distribution, their structure-function relationships with viral envelope proteins or chemokines, and because there are few tools for studying receptor function. We propose to generate additional panels of monoclonal antibodies to all know HIV-1 coreceptors. These antibodies will be used to study receptor distribution and regulation of expression. They can be used in attempts to block HIV-1 infection of virus cell types in order to determine if a given receptor can function as a coreceptor to enable virus strains to enter specific types of cells. These antibodies can be used for structure-function studies and in competition assays to study how env protein interacts with various coreceptors. Specific high affinity antibodies may also have the potential to be used as therapeutic agents in certain circumstances. We propose a collaborative approach in Phase II that utilizes the strengths of R&D Systems and our academic collaborators to develop additional antibodies with several novel approaches. These antibodies will be characterized in a variety of assays, taking advantage of the large panel of chimeric and mutant receptors developed by, as well as the expertise of our collaborators in studying HIV-1, HIV-1-2 and SIV and their coreceptor interactions. PROPOSED COMMERCIAL APPLICATION: We plan to generate panels of monoclonal antibodies to all of the known chemokine receptors/HIV coreceptors. These antibodies will be made commercially available to researches for studies on: (1) the distribution and regulation of expression of these receptors; (2) blocking HIV infections to determine if given receptors can function as coreceptors for infection of specific cell types by various viral strains; (3) the nature of the interaction between env protein and various coreceptors. Specific humanized, high affinity monoclonal antibodies that block penetration of specific cell types by various HIV strains may have the potential to be used as therapeutic agents under particular circumstances.